Garden Detective: Ailing azaleas, fruitless fig tree, curtailing crabgrass

DEAR JESSICA: I have azaleas that have a white crust on their branches that I haven’t seen before. They are not doing well. — Christine Doukas, Lindenhurst

DEAR CHRISTINE: The white masses you're seeing are female azalea bark scales and their egg cases, covered by a protective waxy coating. The spots are not only unsightly, they threaten your plant's health as they suck out its sap. To make matters worse, the insects' sweet, sticky excrement, honeydew, will cover the plant over summer, attracting other pests as well as black sooty mold; the latter is uglier and will further weaken the plant.

Your best course of action is to scrape off as many of the white masses as possible, or prune out heavily affected branches, then spray the plant with horticultural oil before it breaks dormancy. (It’s too late for this now, but I emailed this advice to Doukas early last month.)

For others experiencing this problem, the seasonally appropriate control right now would be scraping and pruning. For heavy infestations, follow this with a soil drench using a product containing the active ingredient imidacloprid; follow package directions carefully, and it should offer protection for the season.

DEAR JESSICA: Someone gave me a fig tree cutting, which I planted in a pot and for two years kept outside, moving into the garage over the winters. In 2018, I planted it outside, on the south side of my house, and the tree produced about a half a dozen edible figs. In 2019, the tree came through the winter nicely and produced about two dozen fruit. Unfortunately, these figs did not develop and never got any larger than big grapes. Please let me know what went wrong and what can be done to prevent a reoccurrence this year. — Felicia Werst, Commack

DEAR FELICIA: Figs are fickle fruit. Many of the available varieties originated in the Mediterranean, where the climate is a lot warmer than in New York. There are cold-hardy types, but even those require an abundance of heat, sun and water during the growing season.

Many backyard growers — myself included — have experienced the frustration of a fig tree covered in hard, inedible, walnut- (or grape-) size fruits that simply don’t ripen. And because figs will not ripen once picked, there’s no hope for them.

The problem sometimes can be attributed to pollination. Some varieties are self-pollinating, but others are not. Since your tree provided fruit in the past, we can rule out this. Other possible culprits include insufficient heat, sunlight and/or water, and, in many cases, winter dieback. If plants are unprotected, their above-ground growth will often die back to the ground over winter, with new growth sprouting from the roots. When this happens, new growth is technically a new plant, which can take years to bear edible fruit.

Ensure the tree gets 1½ inches of water per week, accounting for rainfall. During hot, dry spells, insert your finger 2 inches into the soil daily, and apply water when the soil around the roots is dry. Southern exposures typically get the most sunlight, but not when blocked by trees, fences or other structures. If your fig tree is in the shade, dig up and relocate it before it leafs out.

Overfertilization also can prevent figs from ripening, especially if the tree is planted in a lawn that receives nitrogen applications (if that’s the case, move it). Fertilize the tree once per month from leaf out until mid-July, applying 1 ounce of a balanced 8-8-8 or 10-10-10 product.

DEAR JESSICA: You wrote an article a few months ago about an organic crabgrass prevention application. It had to be applied once in the early season, as the forsythia is blooming. Can you tell me the name of the product? We use Jonathan Green four-step program every year with an extra application of crabgrass control in late July. It hasn’t been very effective. — Lou Giacalone, West Islip

DEAR LOU: The adage “an ounce of prevention is worth a pound of cure” applies to weeds as to life. Crabgrass is best controlled by preventing its seeds from germinating.

This is done using a “pre-emergent” control, and the natural option I wrote about is corn gluten meal. Follow package directions carefully, and, yes, apply it when the forsythia blooms. But be sure to watch the forsythia on your side of the block; the shrubs across the street have a different exposure than your property does, meaning your crabgrass, too, will be on a different schedule. If there are no forsythia on your side of the street, look for some on properties around the block that face the same direction as your house.

The window of effective pre-emergent control begins when the forsythia blooms, and ends when the lilacs fade, so you typically have more than a month to get the job done.